The art of interconnecting circuit points on electronic components and integrated circuit devices with one another using lead wires bonded to those points is called "wire bonding". In the current state of the art the actual bonding is often done using sonic energy applied to one side of the wire while at its opposite side the wire rests on the circuit point or "pad" to which it is to be bonded. It is common to bond aluminum and gold wires in the order of one mil diameter to circuit pads only three or four mils square. In the bonding process, wire stored on a spool has its free end bonded to one circuit point. The bonding tool and the work are moved relatively until the second circuit point and the wire lie under the tool. The tool creates a second bond to complete a wire connection between the first and second circuit points. In the usual case the process is completed by breaking the wire adjacent to the second bond.
One popular expedient is to bend the wire adjacent to the second bond to work harden it at that point. Some embrittlement occurs and that minimizes stretching of the wire and makes it easier to break by pulling. The bonding tool rests on the wire at the second bond while the wire is being pulled to reduce strain on the bond. That method works well only for very fine wires up to about ten mils diameter. Gold is too expensive for use in most applications which require heavier wire. Instead, aluminum is used almost exclusively and the design of bonding tools and techniques is based on the characteristics of that material.
The force required to form bends in heavier wires that are made sharply enough to accomplish work hardening and embrittlement is relatively great. So is the force required to part the wire by pulling. These forces exceed the force with which the bonding tool may be brought to bear on the second bond without altering the tool's primary, bonding function. The obvious alternative is to employ some means to cut the wire but to do that is not without problems. The amount of energy required to accomplish bonding exceeds the energy needed to cut a wire. That and other considerations make it impractical to attempt to make the second bond and to cut the wire in a single operation with the bonding tool. One arrangement which has enjoyed considerable success is to mount a guillotine cutter immediately forward of the bonding tool opposite the wire feed side. Additional operating and control mechanism is required and setup is made more complex but the guillotine is an adequate solution in long run, automatic manufacture. The guillotine is not at all satisfactory when manual search and bond procedures are used because it tends to obstruct the operator's view of the work area and it is to the provision of apparatus and techniques for completing heavy wire circuit connection using manual control of the bonding tool that this invention is addressed.